Experimental investigation and computational validation of heat losses from the cavity receiver used in linear Fresnel reflector solar thermal system

This paper presents the analysis of heat losses from the trapezoidal cavity receiver used in linear Fresnel reflector (LFR) system. The experimental studies are conducted under laboratory conditions that are specially designed for this purpose. The effects of parameters such as the temperatures of the tube surface, depth of receiver, number of tubes, and emissivity of tubes are investigated. The loss of heat is taking place from the tube outer surface to glass cover, below the receiver and then glass cover to ambient. As part of this investigation, the system is modelled and simulated using computational fluid dynamics (CFD). After validation, contribution of convection and radiation to the total heat transfer are found out using CFD. Computational predictions are shown to be consistent with the experimental observations which show that the CFD model is a reliable tool for predicting heat loss and overall heat loss coefficient. It was found that losses due to convection are between 5 and 18% of the total heat losses.

► Inclusion of complete absorber tubes in the analysis of the cavity receiver. ► CFD simulations are carried out using 3D model of the cavity with pipes inside it. ► Modelling includes gap between end tubes and side walls. ► Parametric studies are carried out experimentally as well as computationally.